Method of casting



Nov. 27, 1928.

A. o. AUSTIN METHOD OF CASTING JNVENTOR.

Filed July 1926 Patented Nov. 27, 1928.

UNITED" STATES 1,693,429 PATENT OFFICE.

ARTHUR AUSTIN, OI BABBERTON, OHIO, ASSIGNOB, BY MESNE ASSIGNMENTS, TO THE OHIO BRASS COMPANY, OF MANSFIELD, OHIO, A CORPORATION NEW JERSEY:

Application filed July 2,

This invention relates to the manufacture of ceramic ware and has for its object the provision of a method by which articles of this nature may be more quickly and efficiently manufactured by casting than has heretofore been possible and by which many articles may be cast that heretofore could not be made by this method.

The invention is exemplified in the steps in the process, described in the following specification and illustrated in the accompanying drawing.

In the drawi Fin. 1 is an jevation of half of a mould showing the formed piece and other parts in section.

Many ceramic articles may be formed by what is known as the casting method in which a mould of plaster of Paris or other porous material is filled with sli in which the clay is mixed with Water and t e water allowed to pass by capillary action through the wall of the mould leaving a layer of clay deposited on the inner surface of the mould.

In the formation of ceramic articles by the casting process it is often very diflicult or impossible to form pieces with certain body compositions which will not crack during the casting process. The time required in casting as well as the corrosion of the plaster of Paris moulds used is also another serious objection to using the casting process in many operations. The dissolving or disintegration of the plaster of Paris moulds not only tends to reduce the useful life of the mould, but in many cases causes a change in the casting slip which makes casting exceedingly difficult. In the ordinary casting rocess the mould has to be capable of absor ing water so that the cast piece will build up on the walls of the mould by hardening of the slip due to the absorption of Water. In general, this limits the nature of the material which can be used for forming moulds to plaster ofParis. Since the plaster of Paris is not very stron small pieces breaking oil and getting into t e casting slip or pieces of ware ad's/cent to the mould tend to spoil the properties of the slip so that the casting and burning properties in many cases arematerially changed. The fouling of the casting sli from material absorbed from the moulds an entering the sli directly or through chips from the moul s, or by defective cast pieces which are returned to the slip, is a serious item and causes losses and amnion or casrme.

1926. semi no: 120,090.

irregularities in the casting process. Another difficulty in casting is encountered owing to the fact that the portion of the cast piece next to the mould is'dense while the surface in contact with the casting slip contains a much larger percentage of water. During the dr ing operation the 1portion containing t e larger percentage 0 water tends to shrink more than the denser part which shrinkage is resisted by the portion adj acentthe mould so that in many cases a check or crack develops owing to the stress set up.

The present method is designed to eliminate this difiiculty to a very large extent and at the same time facilitate the casting operation.

Fig. 1 shows one half of a casting mould used in the process to which this invention refers, also a section through the piece of ware or the article being formed. In the ordinary casting process it is necessary to use slips in many cases which will shrink but little during the casting, as it is necessary to keep the cast material in contact with the mould so the capillary attraction will be maintained in order that the piece Will be built up to the desired thickness. Many desirable casting slips can not be used to advantage owing to the fact that the time required in castin is so long that the piece be ins to shrink Iormin air pockets or films tween the surface 0%. the cast article and the mould which destroy'the capillary absorption of the mould. In the improved method this is practicall eliminated or reduced so that it is not a serious factor and permits the use of casting slips which it would not be possible to use in the ordinary method.

In the form of the invention shown in Fig.

1 a steel or metal case 10 with holes 11 for clamping the two halves together is lined 95 with a p aster or other porous lining 12. The inner surface 13 of the plaster conforms to theoutline of the piece 14 which it is desired to form. The particular piece-shown is a bushing, but it is evident that the method may be 100 applied to practically an form of ceramic ware and is particularly a aptable t0 sanitary ware. electrical porcelain or other complicated shapes.

The entrance to the inside of the mould is obtained through pipe connections 15 and 16 which are usually provided. with valves 17 and 18 connected to hose connections 19 and 20. The piece 14: has an undercut on the outer surface, hence it is necessary to use split I rings 21 and 22. While these rings are us ally of the same composition as the mould, they may be made of metal, wax, or other material in many cases. The ring 21 is shown as made of non-absorbent material and covered with an absorbent layer such as a wrapping of cotton tape. Plugs 23 and 24 are used to form the inside ends of the piece to size. 7

While these plugs are usually ofthe same composition as the mould 12 theymay beof non-absorbent material in many cases. Where they are made of absorbent material, the inner ends are 'covered with non-absorbent material 25. In the casting operation the two halves of the mould are bolted together being made to register by dowels 26 which register with holes in the complementary half of the mould case. After the pipes 15 and 16 with the end plugs 23 and 24 arein place,

'the two halves may be clamped together on the slip inside the mould through the pipe; "20 which causes the material to deposit much more rapidly than where the capillary attraction only is used to take out the water and build up the layer of material 14. The jacket 10 permits the use of rather highpressures. With the high pressure it ispossible to maintain contact between the piece 14- and the surface of the mould 12 at all times. This permits the use of slip which otherwise would tend to contract and draw away and also which will have less shrinkage in the drying o eration. In some slips it is not necessary t at pressure be applied in order to make use of the invention. .In general, however, it is foundadvisable-as the time of casting is materially reduced and a mould may be generally used which has much longer life.

When the cast piece has obtained the desired thicwess which is usually determined by time or by noting the increase in the weight of the mould with slip as a whole, the pipe 19 is connected to an air or oil supply which has a pressure equal to, if not slightly greater, than that in the line 20. The valve 1? may tlli'l he opened allowing air or oil to enter which will replace the slip on the inside of the piece. In some cases it is desirable to disconnect the line 20, opening the valve 18 and drawingthe slip 29 out of-the interior of the piece, after which air or oil may be allowed to take its place.

The inner layer of the piece which has been in contact with the slip has a much larger percentage of water. -When, however, the inmakes it possible to build up a dense layer .In'general, it is advisable to use amaterial which will not wet or dissolve the inner-surface'as water would, but one which will tend to'drive out the water and harden the inner surface. When the water on the inner surface hasbeen reduced sufliciently, the pressure may be reduced and the oil removed from the inner surface. In some cases, it

may be desirable to circulate air through the flnner surface in order that the piece maybe 'ven'a slight shrinka e, permitting it to be rawn, more. readily rom the moulds. In many pieces, however, this method permits of makm a piecesufiiciently hard so that it may berea ily removed from the moulds. In very delicate pieces it is frequently possible to fill the interior either partially or wholly with wax in place of oil or air. As the Wax hardens it will form a support for the piece permitting it to be removed from the mould. Where the piece is placed in a warm room w1th a high degree of moisture saturation, the wax may be softened and permit contraction-of the formed piece without damaging the piece.

The method may be applied in many different ways. 'It is important, however, to apply pressure to the inner surface after the form ng 1n order to drive out excess water.

With the arrangement shown in the drawmg, shp may be allow to flow through the piece by regulating the valves 17 and 18. This tends to prevent settling of the slip which is especially important in casting electrical porcelain as resulting dielectric properties of the mixture may be spoiled by the settling operation. Thecirculation of the slip on the inside also tends to cause a more uniform composition on the walls of the piece. -Where the absorbing material of the mould 12 is of a dense composition the absorption may readily be improved by the use which will not readily be dissolved by the water andsalts absorbed from the casting slip. The increased of the use of moulds of greater density than would otherwise be possible.

the moulds themselves ma be made of porous, vitreous material WlllCll has been fired.

. moved from the moulds.

It is evident that by starting the pressure rather low and increasing it that a more uniform density of material will be obtained tantthat the expansion or deformation of the mould for different pressures be given careful consideration. In some cases it is desirable to start at a. much higher pressureand reduce the pressure as the operation proceeds. This is particularl true where the operation requires considera le time so that there is a slight shrinkage the ressure as the operation proceeds, the mou d will contract and take up the shrinkage so that the pressure on the inside of the piece will not cause a tension on the outer layer with the danger of forming a flaw.

In order to facilitate the draining or filling of the mould or cast piece of ware Valves 34 and 35 may be added. The lines to which these valves are connected may be connected to an air or oil supply as desired.

I claim 1'. The method of casting comprising the steps of filling a mould of porous'material with a ceramic ware slip, placing hydraulic pressure on the sli within the mould to facilitate passage 0 water from said slip to said mould, permitting a layer of ceramic material to be deposited on the inner wall of said mould, removing the slip from the mould, and filling the interior of the mould with. a fluid under pressure to compress the deposited layer and render it more nearly uniform.

2. "The method of casting ceramic ware comprising the steps of filling a ceramic slip into a porous mould, permitting a deposit of ceramic material from said slip on the inner surface of said mould, draining the slip from the mould, filling the mould with a liqu d immiscible with water and subjecting said liquid to pressure to compress said layer against the wall of said mould to render said layer more uniform.

3. The method of casting ceramic ware comprising the steps of filling slip mto a porous mould and agitating the slip during pressure possible permits In'some cases,

the liquid placed mould to from the cast piece. It 1s, however, imporf in the piece. By removing deposit of a layer therefrom on the surface of said mould.

4. The method of casting ceramic ware comprising the steps of filling a porous mould with slip, placing pressure on said slip to facilitate'the deposit of a layer therefrom on the surface of the mould and agitating the slip during the deposit of the layer.

5. The method of castin ceramic ware comprising the circulation o slip through a porous mould to permit deposit of a layer therefrom on the surface of said mould.

6. The method of casting ceramic ware comprising the circulation of slip under pressure through a porous mould to permit deposit of a layer of material from said slip on ithesurface of the mold.

- 7. The method of casting ceramic ware comprising circulatin slip through a ceramic ermit the eposit of a layer thererom on t e surface of the mould, removing the slip leaving the deposited layer and exertng pressure on said layer while still in said mould to remove moisture therefrom and render the layer more nearly uniform.

8. The method of casting ceramic ware comprising the steps of introducing slip into alower part of the mould permitting the slip to escape from the upper, part thereof and thereby causing the slip to circulate upwardly through the mould.

9. The method of casting ceramic ware comprising the steps of causing slip to enter at a porous bottom and to escape at the top of the mould, and providing resistance to the escape of the slip to produce pressure on the slip in the mould.

10. The method of casting ceramic ware comprising the steps of introducing slip under pressure into a porous mould, permitting the slip to escape from the mould and offering resistance to escape of the slip from the mould to place the slip in the mould under pressure, thus supplementing capillary action in withdrawing liquid from the slip through the walls of the mould.

11. The method of casting ceramic ware comprising the steps of placing slip under pressure in a porous mould, agitating the slip during deposit of material therefrom on the the inner surface of the mould and forcing the slip from the mould by means of fluid under a pressure sufficient to force the slip from the mould against the pressure thereon.

12. The method of casting ceramic ware comprising the introduction of slip into the lower port1on of the mould, exerting pressure on the slip when the mould is filled therewith, permitting deposit of material from said slip on the Wall of the mould and introducing a liquid under pressure immiscible with the liquid of said ship into the upper portion of the mould, the pressure on said liquid being sufficient to force the slip from the mould against the pressure on the slip.

13. The method of casting ceramic ware comprising the deposit of a layer of material v on the inner face of a porous mould from slip contained in the mould, removing the slip and introducing material to form a core on the interior of the formed layer.

14. The method of casting ceramic ware comprising the deposit of a layer on the inner surface of a mould from slip contained in the mou'ld,and providing a yielding core within the interior of the formed layer.

15. The method of casting ceramic ware comprising the deposit of a layer on the inner surface of a porous mould from slip contained in the mould, and introducing solidifying material into said mould to form a core therein.

16. The method of casting ceramic warereeaaae comprising the deposit of a layer on the surface of a porous mould, from slip held in the mould, withdrawin the slip and introducing material which solidifies into a yielding mass to form a core and exerting pressure on said layer by means of said material.

17 The method of casting comprising the steps of depositing a layer on the inner surface of a porous mould, from slip held in said mould, withdrawing the slip and introducing liquefied wax into the mould to exert pressure on the formed layer and maintaining the wax yielding during drying of said layer. s

In testimony whereof I have signed my name to this specification on this 29th day of June A. D. 1926. ARTHUR O. AUSTIN. 

